1. Technical Field
The present invention, involving bookbinding units that collate sheets conveyed out of a photocopier, printer, or the like, into a bundle and cover the bundle with a cover sheet, relates to improvements in mechanisms for spine-creasing when encasing a bundle of inner-bound leaves with, and binding the bundle into, a cover sheet.
2. Description of the Related Art
With such bookbinding units generally, so-called perfect binding is known, in which sheets that are conveyed out of an imaging apparatus are stacked and collated into a bundle on a tray device, adhesive is applied to the spine part of the sheet bundle and the bundle is joined together with a cover sheet, into its central portion, in the form of an inverted T, and the cover sheet is spine-creased to close it onto the bundle.
In conventional perfect binding techniques of this sort, forming folding scores in the flaps of the cover sheet is known, and is often adopted with thick cover sheets and other in encasing situations in which the cover cannot be readily folded. Traditionally, however, for such folding scores a cover sheet is pressed, as a process prior to bookbinding, to form the folding scores in the cover.
Meanwhile, various bookbinding units which are linked to the discharge outlet of an imaging apparatus and that collate into bundles sheets on which images have been formed, apply adhesive to the bundle spines, and thereafter bind the bundles together with cover sheets have been proposed—such as is disclosed, for example, in Japanese Unexamined Pat. App. Pub. No. 2005-305822 (cf. FIG. 1). This publication discloses an apparatus that stacks and collates into bundles sheets (inner-bound leaves) from an image forming apparatus and applies adhesive to the spine portion of the bundles with an adhesive applicator disposed downstream; the sheet bundles are case-bound into cover sheets readied at (supplied/fed to) the downstream side of the adhesive applicator. Then, the cover sheets are bound on by contacting, in an inverted-T form, the inner-bound sheet bundle onto the central portion of a cover sheet, and spine-creasing the cover sheet with spine-creasing pressing members. Herein, the spine-creasing pressing members (spine-creasing plates in said publication) are configured to fold over and press the cover sheet with a left/right pair of platelike members.
As described above, in bookbinding by collating into bundles sheets conveyed from an image forming apparatus or the like, and applying adhesive to and thereafter binding covers onto the bundles, conventionally, as is the case with the just-cited JP 2005-305822, the shoulder portions of the cover sheet are fold-bended and press-formed. When pressing members for this purpose, such as spine-folding plates, pressure-nip a cover sheet along both shoulders, the adhesive applied to the spine portion can sometimes leak out onto the back side of the cover sheet (the cover rear face). In particular, if excess adhesive is applied to the spine portion, it can leak out to the cover rear face, giving rise to a defectively bound booklet in which inner-bound leaves are adhered to the back side of the cover sheet. Conversely, if an inadequate amount of adhesive is applied to the spine portion, it can become bent along the spine cover when the cover sheet is opened; either case will lead to problems with the quality of the booklet's appearance.
Along with these sorts of difficulties, if paper of thick caliper is used as a cover sheet, with the cover sheet not bending easily in opening a booklet after it has been bound, areas in the spine cover where the adhesive is weak can become bent. To address this, as described above bookbinding techniques whereby folding scores are formed in both flaps of a cover sheet are known. However, this sort of bookbinding technique cannot easily be adopted in a system apparatus such as in the just-cited JP 2005-305822. In particular, conventional folding scores must be press-formed into the cover sheet in advance, which means that in cases where, for example, in a device system for continuous imaging, both the inner-bound leaves and the cover sheets are printed with images, sent to a bookbinding unit downstream, and bound with covers in the bookbinding unit, processing the cover sheets with folding scores in advance places serious restrictions on the device configuration.